Process for fractionating and blending a reformate to obtain a high octane gasoline



Jan. 17, 1961 H. LUTz 2 968,609

PROCESS FOR FRACTIONATING AND BLENDING A REFORMA@ TO OBTAIN A HIGHOCTANE GASOLINE Filed Dec. 30, 1955 vm TR INVENTOR. Irvin h'. LuizW/wQ/w ATTORNEY SINNH'.

United States Patent O PROCESS FOR FRACTIONATING AND BLENDING p AREFORMATE TO OBTAIN A HIGH OCTANE GASOLINE Irvin H. Lutz, Texas City,Tex., assignor to The american Oil Company, Texas City, Tex., acorporation of Texas Filed Dec. 30, 1955, Ser. No. 556,498

5 Claims. (Cl. 208-100) My invention relates to the production of highoctane gasoline from low octane naphthas by catalytic reforming. Moreparticularly, it relates to the production of a high octane premiumgasoline, e.g. at least 98 and more especially 100 F-l (CFR-R) octanenumber or higher, 'and a second gasoline of lower octane number fromgasoline forming and gasoline blending components in a common refinerygasoline pool by an integrated process including selective reforming,fractionation, and blending steps. Y

Conventional practice has been to produce premium gasoline fromcatalytic gasoline, i.e. the gasoline produced iby catalytic cracking ofgas oil. Catalytic gasoline as produced may average 93 to 95 F-l octanenumber clear. Thus, it can be increased in octane, up to lthe 96 to 97F-l level, simply and economically by the addition of tetraethyl lead inamounts up to the legal limit. There has been virtually no incentive todate therefore, except in special situations, to use catalytic reformingfor the production of base stock for premium Igrade leaded gasoline.Although catalytic reforming has been described in numerous patents 'andpublications as -producing very high octane gasolines, actually theinstallation and operating costs for the production of reformate of thenecessary octane quality in the necessary Volume, except for feedstocksof unusual quality, cannot lbe justified for premium gasoline, comparedtothe use of catalytic gasoline and the cost of tetraethyl lead. Hence,catalytic reforming has been used by most refiners to upgrade asnecessary the octane value of lower quality gasolines such as virginnaphthas, -thermally cracked gasolines, coke-still naphthas and the likein the refinery pool, for 'the production of a second structuregasoline, variously 4referred to as regular, house-brand, etc. This hascontributed indirectly howvever to the production of premium gasoline byupgrading the over-all octane level of the refinery gasoline pool and bypermitting the segregation of high quality naphthas necessary to meetpremium octane goals.

In the production of unleaded premium gasoline of higher octane numberthan about 95 F-l, of course it has not been possible to use catalyticgasoline as the major base stock component. Moreover, at 98 F-1 andhigher, even with tetraethyl lead, it is uneconomic or impossible withinlegal lead limits to rely on catalytic gasoline as a major base stockfor premium gasoline. Consequently, as premium octanes reach the 98 to100 F-l level, it has become necessary to consider catalytic reformingon a major scale for the production of premium grade base stocks. Theseveri-ty of reforming required, however, imposes severe economicpenalties. As the octane level.of the C5+ reformate produced isincreased above the 90'to 95 level, depending upon the quality of thecharge stock, yield lossA tends to become excessive. Catalyst life y2,968,609 Patented Jan. 17, 19.61

lice,

converting low octane naphthas to high octane premium gasolinecomponents by means of a process which conserves feed and catalystrequirements and yet produces more octane-barrels of refoimate thanproduced by conventional reforming. The process has special value in theproduction of 100 F-l octane number unleaded premium gasoline. Thenaphtha charge stock is prefractionated, either as an incident to crudedistillation or in special facilities, to obtain a C,{ heavy naphthafraction, more advantageously a C8+ heavy naphtha fraction. The linalboiling point should not exceed 400 F. to any substantial extent becausethe product then will contain an undesirable volume of componentsboiling above the gasoline range. The heavy naphtha charge is subjectedto reforming in the presence of a reforming catalyst and hydrogen to aseverity producing a C54- reformate of at least 93 F-l octane number.Advantageously, the reforming severity exceeds that producing a C5+re,.-

ormate of 95 F-l octane number clear and, in the prof duction of superfuels, may approximate 100 F-l clear. The reformate obtained is split byfractional distillation ata cut point in the range between about. 225and 300". F. to obtain a heavy fraction and a light fraction. AIt hasbeen found that by correlating in a simple manner the cut point with thereforming severity for 'the boiling range of any particular charge stockthat a heavy fraction can be produced by simple fractional distillationcomprising 40 volume percent or more of the total reformate whichcomprises percent or more aromatics. Heavy frac tions so produced havebeen Ifound to have octane numbers of 100+ F-l clear and may be blendedwith light fractions of suitably high blending octane values to producea full boiling range premium gasoline of 98to 100 F-l octane number orhigher. The light fraction split from the reformate is significantlylower in octane num.-` ber than the heavy fraction. It is advantageoustherefore, according to the invention, to reprocess this fraction as byrecycling to the reforming zone but preferably by selective processingin a second conversion stage favoring para'in cyclization and/orisomerization. When the cut point in the splitting operation is such asto include C7s in the light fraction, it may be advantageous, partie,--illarly at .the higher severity levels, to segregate the toluene cut forseparate blending, or for toluene recovery.

The invention thus provides processing means for upgrading the renerygasoline pool to an optimum extent Iby producing premium grade blendingstocks from low octane number naphthas through reforming combined withsegregation of the super octane heavy components of reformate withsuitably high octane light components from extraneous sources, e.g.light catalytic gasoline, lightl alkylate, reprocessed light reformate,etc. The reforming severity burden is significantly reduced compared toconf ventionalV processing requirements. The refinery pool may lbeupgraded further by selective reprocessing and( or segregation of thelow boiling, low octane components of the reformate.I In processing tomaximum octane levels, this provides a substantial yield advantageoverboth once-through and recycle reforming. For example, thejyield of100 F- gasoline base stock from ya blend of the heavy reformate cut froma F-l reformatewith selectively reprocessed lighter components rups 59.10

'to' 100 F-'l orby' extracting'aroma'tics and"recycling' the overhead'by line '13. "Heavier' than '400 'F.-naphtha is 'removed asebottomslthr'o'ugh line 14.

The CH- `naphthais preheated in a 'lir'ed heater '15, and 'in adm'ixture"with recycle gas 'comprising mainly 'hydrogen from'line`1164,`ischarged by line 17 to catalytic reforming 'z'one 18. The inletltemperature `to 'the 'r'eforming'zofne is'in'the rang'eof'about'875f'to l000 F., an'dthe'recycle'gas'ratio comprises'about 2000 to`10,000cubic" fe'etgper "bai-rel'v of charge. 'The charge mixture is contactedin the'r'eform'ing zone with'a reforming catalyst underapressure'in'therange of'about 100 -t0500 p.s.i.g., preferablyin thera'n'g'e "of'about'lSO to 400 p.s.i.g., and at'ta space'velocity in'the range ofabout 0.1to 5.0,' usually about' 0.5 .to' 115,- weight ratio feed perhour to weight ofcatalyst inthe reforming zone. Thereformin'g conditionsarea adjusted' so a'sto provide a severity `producing areforrned product'having'anunleadedF-l roctane number, vafter"stabilition,"of "at least9.3, Jand'preferably -blit v95 sto "98.

'Th'ecatalyst yused in 'thereforniing zone '18 'most advantageously"comprises 'a 'platinum-alumina reforming catalyst. The catalyst is'usually in 'the form of pellets ortblets arranged as a pluralityof'lixed beds disposed in lafseries"of'separate reactors.`Interheating'facilities are rprovided V'between "the reactors tocompensate for endothermic temperature Vdrop through the reformingz'one. Other 'platinum-containing reforming catalysts 'may' be tused,for example, platinum on sintered silicaalumina 'or platinum onhalide'promoted alumina. Also, a @molybdenum oxide-alumina or achromia-alumina catalyst "can be used although 'with less advantage interms of activity a'nds'electivity. These catalysts are readily handled"i'ntnely divided -form 'in a iluidized state, 'thus facilitatingregeneration.

:Because-'of the highreforming'severitis required in the process of theinvention, 'regeneration'facilities for maintaining "thefactivity of`the 'catalyst in reforming zone 18 by tp'erio'dic'burn-off of 'carbon'and oxygen' treatment are desirable. The regeneration process is'not apart of the present invention Vbut will be described briefly. It'may be`conducted periodically or continuously. For examv ple, one or-more ofthe reactors ,can'be taken off-stream,

or the-'unit can'be shutdown, after the catalyst activity has 'dropped'tto a levelre'quiring the use of excessive temperatureslto'obtain thedesired octane quality reformate. 'By providing 'a swing reactor,theunit can be 'operated continuously without shut-down While 'the extrareactor is being regenerated.

The regeneration cycle normally requires "an vinert `gas purging:operation vfollowed by carbon burn-olf with :a dilute oxygen containinggas,e.g. about Zpercent oxygen, to'prevent .undue temperature rise -ata-relatively'moderate temperature in thezrange of about 700 to 900 F.Following the carbon burn-off, vthe catalyst is advantageouslyrejuvenated by treatment with oxygen or enihed air 'ata partial pressureof oxygen exceeding 0.4 atmosphere 'andat a temperature in the range ofabout V950 to 1150 F., Zfor 'a period of time suflicien't tores't'ore'the c'atalyst'to the'virgin 'activity ','level or higher.

"When the catalystis handled in fluidized form, as is preferred :ijn'the case 'of molybdenum oxide-alumina 'cataflowing a stream of spentcatalyst from the reactor to ithe' regenerator for'carbon'burn-oif' withair4 at 900"t`o From catalytic reforming zone 18, the charge mixture ispassed via line 19 to high pressure separator 20. Recycle gas isseparated through line 21 for recycle via compressor 22, line 23, heater24 and line 16. Excess gas can be vented through line 21a. The liquidstream separated in separator 20 is removed through line 25 tostabilizer 26. The stabilizer.zisequipped with reboiler 27. Cgs andlighter `hydrocarbons are removed overhead through '-line 28, `and in"lsom'e" 'cases fit V"may -be desirable to include isopentane inthestabilizer overhead.A The stabilized reformate is passed by line 29 tosplitter tower 30. Splitterf30lisequipped 'with 'a-rebo'iler31. 'Thetower is'operatedrso asito-take overhead throughy line' 32 a lightreformate fraction which contains the Cei hydrocarbons and lighter"and,r"d epending upon the=severity of operation, part or.V all Vof ltheC7 fraction and part of the C8 fraction. y'Theheavy reformate is removedas bottoms through line 33, and advantageously is rerun in tower 34 toremove as bottoms via connection 35 hydrocarbons boiling'higher than the[gasoline endpoint, i.e. 400 lto 415 'The heavy reformate productistreamis'recovere'd asoverhea'dv through line'50 and ispumped to'storage orblending facilities via connectionSl. Ultimately, 'as indicated by line52,the heavy-reformate is blended'to'-specication octane and volatilityproperties with at least 'one"hi`gh"'octane numberlight stock, which maycomprise reprocesse'd light material as irldicatedby li'n'es^ 53 and' 54(see below).

The light reformate `produced according toftheprocess of the inventionvmay 'be @passed 'to .storage 'or Ablending via line 32abutadvantageously is passed by lines "36 and 37'to a repro'eessingzone38'for'further upgrading by selectivetreating. V'Forvexample, the lightfractionncan be rer'unin a second pass'catalyticreforming'zone. Thesame'or a 'different catalyst asthat used in 'catalyticreforming 'zone18 may be'used,'but advantageouslythe conditions ofreforming'are'favorable to paraflin'isomerization anddehydrocyclizationso Vas'to obtain optimum octane improvement Without 'excessive stockloss. For example, W'ith a severity in zone 18 lproducinga 9'8"0 1`00'F1octane 'number reformate clear at 300 p.s.i.g., a'severity 'producinga'reformate inthe range'of 92 may be employed in zone 38'at 200300p.s.i.g.- d

Alternatively, the light -fraction, lpreferably after dehexan'ization,'can'betreated in the presence'of a dehydrocyclization catalyst such asallialized chromia-alumina or in thepresence'of 'an isomeri'zationcatalyst nsuch as aluminum chloride. Furthermore, vthe light fraction4can be further fractionated, as bysol'vent'extraction oradsorpti'on-toseparate'paraiins 'and aromatics,'prior to'reprocessingthe'parains for octane upgrading. `If the'Q, fraction isvvsegregated, it can be processed for benzene recovery. Wherethis'islundes'irable, it-may'be advantageous to '-segreg'ateatoluene cut(200 F. to the reformate vcut-point) for .toluene extractionand-dehydrogenate'the C5- (200 F.-) "fraction to produce a light oleinicgasoline blending stock. The dehydrogenation can "be YsuitablyVandeconomically accomplished by rerunning in -a catalytic'cra`ckin`g'unit, v particularly where facilities Vareiprovidedv for'splitting 'catalytic gasoline into light and heavy fractions. .'Ifdesired "the light .fraction can 'be 'thermally'refor'med Also, lthelight fraction, or apportionthereofjrray 'befrecycled'via connection. toreformingz'o'n'e .18. "'Lig'ht components of virginanaphtha which 'are'not suitable'for'cl'larging to reforming Zone 18 c'anjbe "combined 'a'sby'line d40 withlthe'light reformate for processing under 'conditionsmore selective for upgrading 'liglt hydrocarbons. vides "ahighly'ilexible process for .upgrading the gasoline pool while providinganreconomical source ofheavy high octane `Qmm'p'mients for premiumgasoline of 100+ oc-. tan'e'qulity.

Thus, the yinvention .pro-` Operation according to the invention will bemore specifcally illustrated by means of the following example in whichthe feed stock comprises a 200 to 436 F. heavy naphtha of 51.4 APIgravity and 0.024 weight percent sulfur content. Typically it contains14 percent aromatics, 52 percent naphthenes and 34 percent paraflins(all by volume), and has an octane number of 46.7 F1. The stock istreated in a fixed bed reforming system in the presence of a catalystcontaining 0.6 weight percent platinum on an alumina base and in theApresence of hydrogen recycle gas supplied at a rate of 5000 s.c.f./bbl.The reactor inlet temperature is 930 F. and the average pressure is 340p.s.i.g. The space velocity is about 1.5 weight of feed per hour perweight of catalyst.

The separation conditions in high pressure separator Z are 105 F. and235 p.s.i.g. Stabilizer 26 is operated with a reflux ratio of 3.5 (hot),with an overhead temperature of 142 F., and a pressure of 140 p.s.i.g.The reboiler temperature is 405 F. at 150 p.s.i.g. The C5 to 400 F.reformate charged to splitter tower 30 as an F-l number of 98.2. Acomparison of the `distillation data on the feed to the reforming zoneand the C54- reformate charged to the splitter tower is shown in TableI.

TABLE I ASTM Distillation, F., Vol. Percent Distilled Reformate (Toppedto 400 F.)

The splitter tower contains about 40 theoretical trays and is operatedat 45 p.s.i.g. (tower top) and a reflux ratio of 0.85` r./d. (hot). Theoperating conditions in rerun tower 34 are 355 F. overhead (atmosphericpressure) and 495 F. bottoms.

With the reformate of 98 F-l octane, the toluene fraction advantageouslyis included in the heavy reformate fraction separated in the splittertower. Under these conditions, the overhead temperature is about 260 F.and the bottoms temperature is about 425 F. The yield of heavy reformateis vapproximately 70 volume percent. By increasing the overheadtemperature to about 285 to 290 `F., and with a bottoms temperature 445F., most of the toluene fraction is taken overhead. A comparison oftypical yield and octane data for the two operations follows:

The-octanes were 76.6 and 82.8 F-l, and the ASTM distillation rangeswere 104 to 220 F. and 105 to 247 F., respectively for the lightfractions.

` Hence, high yields of very high octane number reformate, above 100 F-lclear, can be obtained by the process of the invention without requiringexcessive severity in the reforming zone. The light components rejectedare replaced with components of higher octane number from the refinerypool, c g. light catalytic gasoline, polymer gasoline or light alkylate.The rejected light components may be blended to regular gasoline, or maybe reprocessed selectively to higher octane level. Savings with tion of100 octane gasoline by operating at about the.

93 octane level rather than at the 100 level. Also, there is a markedfall-olf in yield as reforming severity is increased. For example, inreforming the naphtha described in the above example, the loss in C54-yield in going from the F-1 level to the 90 F-l level is only` about 5%,but the yield loss is doubled in going from to 100 octane.

The investment and operating costs for installing the invention aremoderate, and in some cases can be reduced to very low values byintegration with existing or conventionally employed fractionatingfacilities such as prefractionators or wet gas absorption towers and thelike. Nevertheless, I have found that there is a breakpoint in theadvantages obtainable with the invention as the se- Verity in thereforming step exceeds that producing about 93 to 95 reformates as forthe production of 100 octane clear reformate. As reforming severityincreases, elimination of non-aromatic components is eifected, increasing octane. In relation to yield, or barreloctanes, however, theresulting benefit is increasingly counterbalanced by non-selectiveproduction of light components, particularly Css and Ces, representingonly marginal gain as straight-through severities are increased aboveabout 9,3..

This seems to correlate satisfactorily, in the contemplation of theinvention, with the decline in catalyst life, so that as octanes spiralhigher and demand higher overall severity, the advantages alforded bythe invention increase.

The actual severity limit for feasibility in any particular case isrelated to the nature of the feed stock as well as the cut-point in thesplitting operation. The more highly paraiiinic naphthas such as certainMiddle East naphthas may require more severe conditions to reach the 90to 93 level than are required `with more naphthenic naphthas such asMid-Continent naphtha. Lighter boiling naphthas suifer greater yieldlosses for the same octane improvement over the 90 to 93 level thanheavier naphthas, i.e. CB-lnaphthas.

As reforming severity is increased to obtain higher than 95 F-lreformates, there appears to be selective conversion of high boiling lowoctane materials to high octane aromatics boiling in the heavy range.The increase in octane of the heavy fraction is almost equal to theincrease in the octane of the total reformate, provided the cutpoint forthe splitting is properly correlated. Thus, as the octane of the totalreformate is increased from the 96 level to the 100 F-l level, the C7+fraction increases in octane number from about 100 to 103, and the Cs-I-fraction increases to about F-l octane. This is obtained at a levelWhere octane improvement is most diflicult. Moreover, there is asubstantial increase in the volume of C8 aromatics relative to otheraromatics as the octane of the total reformate is increased from the 93to 100 F-l level. On the contrary, the octane of the C5 to 220 F.fraction changes very little with total reformate octane. For example,octanel is increased from 73.6 to only 76.6 F-l when the octane of thetotal reformate is increased from 93 F-l to 100 F-l. There iscomparatively greater improvement in C5 to 270 F. octane, from 75.1 to83.1, because of increased production of toluene, but the level is stilllow.

Test data comparing the effect of severity on a typical naphtha chargeboiling in the range of 222 to 424 P. and having an F-l octaneof 45follow: t

TABLE II Properties of reformates TBP-IBI IBP 140 190 205 225v 239 254302 398+ des TBP-FE1' 140 190 `205 225 239 254 302 39s octane severity92.0 F-1 V01.Per`centofout s 8.9 4.2 4.0 9.4 3.0 25.1 30.5 5.2 1.7Percent Aromatics 13.9 2.1 20.8 01.7 9.5 62.6 78.0 93.9

Octane Severity 96.6 F-l Vo1.1 ercentef0uts4 8.0 3.0 2.8 10.9 10 24.727.0 5.8 8.4 Percent Aromatics 20.4 2.7 13.8 74.8 20 3 74.9 87.8 93.1

' octane seeerity 99.3 F-1 Vo1.PercentofCut 9.3 11.0 42.13 2.1 9.6 0.825.8 27.0 5.2 6.4 Percent Aromatics 22.4 9.2 22.9 78.7 38.9 84.4 95.296.3

The cutpoint also depends upon the boiling range of the feed. The costof obtaining octane appreciation by Vreforming C7 to C8 components to100 F-l octane is very high compared to the cost of obtaining octanes byreforming to 92 F-l and separating the Cq-lfraction. The increasedseverity appears to increase hydrocracking to an extent thatthe octanegain is obtained at the expense of excessive loss of hydrocarbons to thelighter than gasoline range. By comparison, reforming heavy naphthasv to100 F-l ishmuch moreattractive. Consequently, it is advantageous toprefractionate the charge naphtharto eliminate the C7 fraction from thefeed, and for maximum advantage, split the reformate correspondingly.However, at the higher severity. levels, the increase in tolueneconcentration justifies its inclusion in the heavy reformate.

The composition of the feed, as noted above, also may beV a factor indeterminingthe severity level at which reformate splitting becomesattractive. Thus, in running a highly paraiiinic naphtha such asa'Kuwait naphtha, the yield fall-off with increasing reformate octane issuch as to impose a limit of about 92 to 93 F-l clear. With stockscontaining higher percentages of naphthenes such as Mid-Continentnaphthas, the operation is most attractive as reformate octane exceeds95 F-l. Also, with mixed feeds such as blends containing thermallycracked or catalytically cracked heavy naphthas, it may be desirable tolimit the severity to about the 92 to 95 F-l range.

The cutpoint in splitting'also should b e correlated with the propertiesof light stocks available for premium gasoline blending. Thus, to obtainthe` maximum benefit of theinvention, it is advantageous to cut at -aslow a tem perature, providingl about 80% aromatics or more in theheavyreformate, as will permit replacement of the light components separatedwith higher octane light components from thegasoline pool. A suitableexample of the -latter is a light fraction separated from catalyticgasoline which'l includes all of the amylenes and enough ofthe Cs andCqs to provide afull range gasoline, after blendingwith Athe heavyreformate and added butanes to octane specification, without exceedingthe maximum seasonal Reid vapor pressure. The light catalytic gasolinewillhave an F-l octane rating approximately 3 to 5 numbers higher thanthe total catalytic gasoline since the amylenerfraction, usuallycomprising upto about volume percent of the total catalytic gasoline,has an Fl octane exceeding 100. Thus, for example, a 25% by volume cuton total catalytic gasoline of 93.3 F-l octane has an octane of 97.6F-l. Other high .octane light components of suitable volatility forblending withr the heavy reformate include light alkylate, particularlytechnical ethylene alkylate produced by alkylation of aluminumchlorideisomerization of C5-C parafns, light olen fractions such asdi-isobutylene, and the like. Several illustrative gasoline blendsfollowc.

The invention thus provides aY feasible and relatively economical meansfor producing Vpremium Vgasolines of 100 F-l clear octane and higher.These ratings, of course, can be `improved by the addition of tetraethylleadto an extent determined by the response of the particular blend tooctane appreciation by this means. In blending, advantages in yield ofhigh octane gasoline can. be obtained at the higher reforming severitiesin conjunction with splitting as indicated by Athe following dataindicat.v

ing the yield in barrels of 100 F-l octane gasoline per 100 barrels offeed obtained by blending heavy reformate with 93.3 F-l catalyticgasoline.

' Heavy Reformatc Yield, Total Reformate F-l bbls./100

' bbls. feed Percent F-l 99.7; 50.5 102.5` es 101.5 l47 Y104.9A 81Expressed somewhat differently, the availability of high octane blendingstock from reformate for super octane fuels decreases rapidly as thereforming severity is re-V duced below the 95 to 100 F-l level The yieldof 9.8-

octane clear blending stock from 95-0ctane reformate is 80%, but if thetotalreformate splitis only 90-octane, the availability of 98octaneblending stock drops t0. 57%. The advantage in selectivity of platinumcontainking reforming catalysts isrindicated by comparison of these datawith the yield of 98-,octane blending stock from 90-octane reformatefrom fluid molybdenum oxide-pV alumina reforming which is only 50%.lFrom 85V-octa'ne platinumA reformate, the yield ise37 fromcorresponding moly. reformate, the yield is almost zero.. If 98-octaneblending stock is produced by straight reforming molybethylene withisobutanein the presence of. aluminum chlo.

dena type catalyst to 9S-octane, the yield is 65% on the.

feed. If the 98-octane stock is produced by fractionating -octane.reformate, the yield is 55% on feed while a distillate `fraction ofkabout 20% on feed, rating about' .182 to 84 octane number clear, isproduced in addition for blending to regular gasoline or for selectiveprocessing. Since the light reformate characteristically shows good leadresponse, its use in upgrading regular leaded gasoline is valuable or itcan be blended to 91-96 aviation gasoline. In effect, therefore, theyield of liquid product has been increased by a minimum of 10% throughan advantageous exchange of the lower octane light components of thereformate with higher octane light hydrocarbons available in the pool.At the same time, reforming severity has been reduced with resultingcatalyst savings. If a 100+, rather than 98, octane stock is producedthe resultant advantages are increased significantly.

In the operation of the invention, high yields of high octane stocks areproduced at maximum throughput in contrast to conventional reforming orproposed methods of recycle reforming. Compared to the latter,conversion of both high and low boiling components is more p selective,for the severity of recycle treatment on unconverted paraflins resultspredominantly in hydrocracking with resulting losses from the gasolinerange and in an undesirable production of light gasoline componentswhich inherently degrade the octane level of the high octane pool so asto limit the volume of 100+ gasoline which can be produced. Selectivehandling of the light fractions to produce benzene, toluene and lightaromatics, or isoparaflins by isomerization, is facilitated. Thus, theover-all octane of the refinery pool can be raised to the optimum extent(or chemicals production increased) while maximizing the production ofsuper octane premium fuel.

I claim:

1. In the production of high octane premium gasoline and a secondgasoline of lower octane number from gasoline forming and gasolineblending components of a common refinery gasoline pool, a process forproducing 100 octane and higher octane full boiling range premiumgasoline from low octane naphthas, which process comprises charging aheavy naphtha charge boiling within the range of C7 hydrocarbons toabout a 400 F. end point to a catalytic reforming zone containing aplatinumalumina reforming catalyst, subjecting said charge in saidreforming zone to a combination of conditions, including a temperaturein the range of about 875 to 1000 F., a pressure in the range of about100 to 500 p.s.i.g., a hydrogen recycle gas ratio in the range of about2000 to 10,000 cubic feet of gas per barrel of charge and a spacevelocity in the range of about 0.1 to 5.0 weight ratio charge per hourto weight of catalyst in said reforming zone, providing thereby aseverity suicient to produce a reformate having a C+ octane number of atleast about 93 F-l (clear), charging said reformate to a fractionatingzone, splitting said reformate in said fractionating zone at a cut pointwithin the range of between a maximum of about 300 F. and a minimum ofabout 225 F. according to the relationship wherein said cut point isnear said maximum of 300 F. when the C5+ octane number of said reformateis about 93 F-l (clear) and said cut point is decreased within saidrange, thereby increasing the yield of the hereinafter designated heavyfraction above a minimum of at least about 40 volume percent of thetotal C5+ reformate, towards said minimum cut point of about 225 F. asthe severity ot reforming is increased to provide a reformate having aC5+ octane number of at least about 100 F-l (clear), whereby twofractions are recovered constituting a light fraction boiling below saidcut point and a heavy fraction boiling in the range of said cut point tothe end point of said reformate, and whereby said heavy fractioncomprises at least about 40 volume percent of the total C5+ reformateand contains at least about volume percent aromatics and has an octanenumber of at least about 100 F-1 (clear), and thereafter blending saidheavy fraction with an extraneous light fraction of high blending octanenumber in proportions suiiicient to produce a full boiling range premiumgasoline of at least about 100 F-l octane number.

2. In the production of high octane premium gasoline and a secondgasoline of lower octane number from gasoline forming and gasolineblending components of a common refinery gasoline pool, a process forproducing from low octane naphthas a full boiling range premium gasolinehaving an octane number of at least about 100 F-1, which processcomprises charging a heavy naphtha charge boiling in the range of C7hydrocarbons to about a 400 F. end point to a catalytic reforming zonecontaining a platinum-alumina reforming catalyst, subjecting said chargein said reforming zone to a combination of conditions, including atemperature in the range of about 875 to 1000 F., a pressure in therange of about 100 to 500 p.s.i.g., a hydrogen recycle gas ratio in therange of about 2000 to 10,000 cubic feet of gas per barrel of charge anda space velocity in the range of about 0.1 to 5.0 weight ratio chargeper hour to weight of catalyst in said reforming Zone, providing therebya severity sufficient to produce a reformate having a C5+ octane numberof at least about 93 F-l (clear), charging said reformate toa'fractionating Zone, splitting said reformate in said fractionatingzone at a cut point within the range of between a minimum of about 225F. and a maximum of about 300 F., wherein two fractions are recoveredconstituting a light fraction boiling below said cut point and a heavyfraction boiling in the range of said cut point to the end point of saidreformate, and whereby said heavy fraction comprises at least about 40volume percent of the total C5+ reformate and contains at least about 80volume percent aromatics and has an octane number of at least about 100F-l (clear), selecting said cut point depending upon the severity ofreforming said charge as evidence by the 05+ octane number of saidreformate, wherein said cut point is selected in the upper portion ofsaid temperature range when the C5+ octane number of said reformate isabout 93 F-1 (clear) and said cut point is decreased within saidtemperature range, thereby increasing the yield of said heavy fractionabove said minimum of at least about 40 volume percent of the total C5+reformate, to said minimum cut point of about 225 F. as the C5+ octanenumber of said reformate is increased above about 93 F-l (clear) towardsat least about 100 F-l (clear), and thereafter blending said heavyfraction with an extraneous light fraction of high blending octanenumber in proportions sufficient to produce a full boiling range premiumgasoline having an octane number of at least about 100 F-l.

3. The process of claim 1 wherein said heavy napththa charge boilswithin the range of C8 hydrocarbons to about a 400 F. end point.

4. The process of claim 1 in which the severity in the reforming zone issucient to produce a C5+ reformate of at least 95 F-l octane numberclear.

5. The process of claim l in which the severity in the reforming zone issufficient to produce a C5+ reformate of at least F-l octane numberclear.

References Cited in the file of this patent UNlTED STATES PATENTS

1. IN THE PRODUCTION OF HIGH OCTANE PREMINUM GASOLINE AND A SECONDGASOLINE OF LOWER OCTANE NUMBER FROM GASOLINE FORMING AND GASOLINEBLENDING COMPONENTS OF A COMMON REFINERY GASOLINE POOL, A PROCESS FORPRODUCING 100 OCTANE AND HIGHER OCTANE FULL BOILING RANGE PREMIUMGASOLINE FROM LOW OCTANE NAPHTHAS, WHICH PROCESS COMPRISES CHARGING AHEAVY NAPHTHA CHARGE BOILING WITHIN THE RANGE OF C7 HYDROCARBONS TOABOUT A 400*F. END POINT TO A CATALYTIC REFORMING ZONE CONTAINING APLATINUMALUMINA REFORMING CATALYST, SUBJECTISNG SAID CHARGE IN SAIDREFORMING ZONE TO A COMBINATION OF CONDITIONS,S INCLUDING A TEMPERATUREIN THE RANGE OF ABOUT 875* TO 1000* F., A PRESSURE IN THE RANGE OF ABOUT100 TO 500 P.S.I.G., A HYDROGEN RECYCLE GAS RATIO IN THE RANGE OF ABOUT2000 TO 10,000 CUBIC FEET OF GAS PER BARREL OF CHARGE AND A SPACEVELOCITYS IN THE RANGE OF ABOUT 0.1 TO 5.0 WEIGHT RATIO CHARGE PER HOURTO WEIGHT OF CATALYST IN SAID REFORMING ZONE, PROVIDING THEREBY ASEVERITY SUFFICIENT TO PRODUCE A REFORMATE HAVING A C5+ OCTANE NUMBER OFAT LEAST ABUT 93 F-1 (CLEAR), CHARGING SAID REFORMATE TO A FRACTIONATINGZONE, SPLITTING SAID REFORMATE IN SAID FRACTIONATING ZONE AT A CUT POINTWITHIN THE RANGE OF BETWEEN A MAXIMUM OF ABOUT 300*F. AND A MINIMUN OFABOUT 225*F. ACCORDING TO THE RELATIONSHIP WHEREIN SAID CUT POINT ISNEAR SAID MAXIMUM OF 300*F. WHEN THE C5+ OCTANE NUMBER OF SAID REFORMATEIS ABOUT 95F-1 (CLEAR) AND SAID CUT POINT IS DECREASED WITHIN SAIDRANGE, THEREBY INCREASING THE YIELD OF THE HEREINAFTER DESIGNATED HEAVYFRACTION ABOVE A MINIMUM OF AT LEAST ABOUT 40 VOLUME PERCENT OF THETOTAL C5+ REFORMATE, TOWARDS SAID 3 MINIMUM CUT POINT OF ABOUT 225*F. ASTHE SEVERITY OF REFORMING IS INCREASED TO PROVIDE A REFORMATE HAVING AC5+ OCTANE NUMBER OF AT LEAST ABOUT 100F-1 (CLEAR), WHEREBY TWOFRACTIONS ARE RECOVERED CONSTITUTING A LIGHT FRACTION BOILING BELOW SAIDCUT POINT AND A HEAVY FRACTION BOILING IN THE RANGE OF SAID CUT POINT TOTHE END POINT OF SAID REFORMATE, AND WHEREBY SAID HEAVY FRACTIONCOMPRISES AT LEAST ABOUT 40 VOLUME PERCENT OF THE TOTAL C5+ REFORMATEAND CONTAINS AT LEAST ABOUT 80 VOLUME PERCENT AROMATICS AND HAS ANOCTANE NUMBER OF AT LEAST ABOUT 100F-1 (CLEAR), AND THEREAFTER BLENDINGSASID HEAVY FRACTION WITH AN EXTRANEOUS LIGHT FRACTION OF HIGH BLENDINGOCTANE NUMBER IN PROPORTIONS SUFFICIENT TO PRODUCE A FULL BOILING RANGEPREMINUM GASOLINE OF AT LEAST ABOUT 100 F-1 OCTANE NUMBER.